The present invention relates to an illumination member with a diffuser.
An illumination member is frequently used in order to uniformly illuminate transmissive liquid crystal displays (LCDs) in particular. There, the light from preferably one or more laterally arranged light sources is directed into the diffuser which acts as a photoconductor. The aim is to have the light as uniformly distributed as possible over the entire output face with a good efficiency. This results in a relatively large design, which seems less suitable for use in flat LC displays. Particularly in motor vehicle displays or in car radios, a thick illumination member is not suitable for an LC-display due to spatial constraints.
The illumination member according to the present invention with the distinguishing features of the main claim has the advantage that the diffuser is designed to be only a few millimeters thick and still emit a homogeneously distributed luminance on its output face. Together with an LC display, the entire unit is only a few millimeters thick so that it is preferably usable also in a motor vehicle display or in a car radio. Due to the simple and flat structure, moreover, the manufacturing costs are comparably low advantageous manner. Due to the low loss of the diffuser, moreover, a favorable efficiency is achieved for the illumination.
The efficiency of the diffuser is further improved by arranging reflectors on one or more of the sides of the diffuser which do not border on the output face. This directs the scattered light in the direction towards the output face so that a further improvement in the efficiency is achieved.
The good efficiency of the diffuser is achieved basically by distributing diffusing transparent spheres or particles having a different refractive index than the diffuser into the photoconductor. The light is advantageously deflected and diffusely distributed in this manner in the boundary junction between the photoconductor and the spheres or particles.
Preferable light sources are lamps, tubes or light-emitting diodes since they are conventional.
If the light source is arranged on a face of the diffuser, the thickness of the diffuser is not increased by the arrangement of the light source. Moreover, the light source can be easily replaced during repair.
Such an illumination member is suited preferably for illuminating a display or a control panel or a symbol illumination. Particularly with the illumination member, a transmissive LC display can be illuminated since the LC display alone does not emit any light.
It is particularly advantageous that the light sources are powered from a control unit so that when the display or a control element is touched, the light sources are made brighter for a specified time.
This is particularly important when used in a motor vehicle. For example, during night travel, the normal brightness of the display can be relatively dark (sleep mode) to avoid blinding (distracting) the driver. When a control element or an appropriate sensor in the display is touched, the luminance is increased for a specific time so that the display is more clearly visible. After the operating function is completed or the specific time elapses, the display can then switch back to sleep mode. The safety in the vehicle is thus increased in an advantageous manner.